can I reclaim a deleted text on an iphone 4?

Restore from your backup, if that text was included in that backup.

There is no trash can to recover text message.

From an iPhone backup that contains the deleted SMS...you would restore your phone from that backup. If not in your backup, it is gone.

You'll lose everything. But you'll get it back if you have a backup. http://support.apple.com/kb/HT1766

Before you restore have you ever backup your phone before? see above link.

Everything that's currently on your phone will be erased. The only data you'll get back is whatever data is in the backup you restore from.